1. Field of the Invention
The present invention relates to a toner for developing electrostatic latent images in full-color image forming apparatus, electrostatic recording and electrostatic printing, such as full-color electrostatic copiers and full-color laser beam printers, and to a developer, a toner container, a process cartridge, an image forming apparatus and image forming method using the toner.
2. Discussion of the Background
Recently, the toner is required to have a small particle diameter and a sharp distribution thereof to produce images having higher quality. In the image forming apparatus forming full-color images with a toner having plural colors, a fixing oil such as a silicone oil is applied or impregnated to the fixer such as a heat roll and a pressure roll to prevent an offset development and smoothly separate a recording paper from the fixer. Further, the full-color image forming apparatus is required to have a smaller size and a lower cost, and to have an oilless fixer without a fixing oil applicator.
However, when a toner image is fixed on a transfer paper by a contact heat fixing method such as an oilless heat roll fixing method and a belt fixing method, the melted toner transfers to the fixing roller and fixing belt. The transferred toner adheres to the following transfer paper again to cause an image noise, i.e., an offset phenomenon. In addition, no oil applicator makes it difficult to separate the recording paper from the fixer. This is worse when a toner having a small particle diameter is used.
In order to solve this problem, methods of adding a release agent to a toner is disclosed. For example, Japanese Patent No. 3270198 discloses a toner comprising a binder resin, a release agent, a colorant and an external additive has an adherence not greater than 0.015 dyne at a contact point by perpendicular tensile fracture after application of a load of 1 kg/cm2 thereto. The release agent is a carnauba wax, which tends to be a fibrous island in a sea and island structure inside the toner when used alone, and difficult to exude on the surface thereof.
Japanese Laid-Open Patent Publication No. 8-050367 discloses a toner comprising a binder resin, a colorant and a wax composition, wherein the wax composition comprises an ester wax having a maximum value in a range of from 350 to 850 and from 900 to 4,000 in a GPC molecular weight distribution. However, the ester wax tends to be a spherical or a spindle-shaped island in a sea and island structure inside the toner when used, and largely dependent on a heat and easy to exude on the surface thereof when heated.
On the other hand, in order to downsize the full-color image forming apparatus, the image developer needs to be downsized. This is because the full-color image forming apparatus needs four image developers containing a cyan developer, a yellow developer, a magenta developer and a black developer respectively. In order to downsize the image developer, non-magnetic one-component developer has an advantage because a stirrer stirring a toner and a carrier is not necessary. However, the non-magnetic one-component developer tends to adhere to developer bearers or regulators. A toner including a instantly melting binder resin for producing fill-color images tends to have this problem, and particularly a toner including a release agent does.
Because of these reasons, a need exists for a toner having good offset resistance and separability, not filming over photoreceptors, and scarcely adhering to the developer bearers or regulators even when used as a non-magnetic one-component developer.